This topic describes the scenarios and limits of cross-region replication.

Cross-region replication enables the automatic and asynchronous replication of objects across buckets in different OSS data centers (regions). It synchronizes operations such as the creation, overwrite, and deletion of objects from the source bucket to the destination bucket. This feature meets users' data replication requirements, and provides an ideal cross-region disaster recovery method for buckets. Objects in the destination bucket are exact replicas of objects in the source bucket. They have the same object name, object metadata, and content, such as the creation time, owner, user metadata, object ACL, and object content.
  • After cross-region replication is enabled, cross-region traffic is generated when you replicate objects between buckets in the primary and secondary regions. OSS charges fees for the traffic occurred during cross-region replication. Each time an object is synchronized, OSS counts the number of requests and calculates the charges on a Pay-As-You-Go basis.
  • For more information about regions that support the cross-region replication feature and the pricing, see the "Cross Region Replication" section in Object Storage Service Pricing.


Cross-region replication can be configured for a wide range of scenarios:

  • Compliance requirements: Although OSS stores multiple replicas of each object on physical disks, the replicas must be stored at a certain distance from each other to comply with regulations. Cross-region replication allows you to replicate data between geographically distant OSS data centers to satisfy these compliance requirements.
  • Minimum latency: You have users who are located in two geographical locations. To minimize latency when accessing objects, you can maintain replicas of the objects in OSS data centers that are geographically closer to users.
  • Data backup and disaster recovery: You have high requirements for data security and availability, and want to explicitly maintain replicas of all written data in a second data center. If one OSS data center is damaged in a catastrophic event such as earthquake or tsunami, you can use backup data from the other data center.
  • Data replication: For business reasons, you may need to migrate data from one OSS data center to another.
  • Operational reasons: You have computing clusters in two different data centers that analyze the same set of objects. You may choose to maintain object replicas in these regions.

Implementation modes

Implementation mode Description
Configure cross-region replication A user-friendly and intuitive Web application
Java SDK SDK demos in various languages


Cross-region replication supports the synchronization between buckets that have different names. If two buckets are in different regions, you can use this feature to synchronize the data from the source bucket to the destination bucket in real time. This feature now offers the following capabilities:

  • Real-time data synchronization: This feature monitors data addition, deletion, and modification in real time and synchronizes these changes to the destination bucket. For objects no more than 2 MB in size, data is synchronized within a few minutes to ensure data consistency between the source and the destination.
  • Historical data migration: This feature synchronizes historical data from the source bucket to the destination bucket, providing two identical data replicas.
  • Real-time display of synchronization progress: This feature displays the last synchronization time for real-time data synchronization and the percentage of synchronization for historical data migration.
  • Easy configuration: The OSS console provides easy-to-use GUIs for configuration management.
  • Mutual synchronization: You can configure data synchronization between Bucket A and Bucket B to enable mutual data synchronization.


  • You can still perform operations on buckets that are being synchronized. However, an object that is replicated from the source bucket may overwrite an object that has the same name in the destination bucket. Exercise caution when you synchronize data.
  • Cross-region replication is an asynchronous process. Based on the size of the data, it usually takes several minutes to several hours to copy data from the source bucket to the destination bucket.
  • Cross-region synchronization applies only when no synchronization to or from a third bucket is enabled for the two buckets to be synchronized. For example, if you synchronize data from Bucket A to Bucket B, you are not allowed to synchronize data from Bucket A to Bucket C, unless you delete the configuration to synchronize data from Bucket A to Bucket B. Similarly, if you synchronize data from Bucket A to Bucket B, you are not allowed to synchronize data from Bucket C to Bucket B.
  • Synchronization is supported only between two buckets in different regions. You cannot synchronize data between buckets in the same region.
  • Currently, the bucket cross-region replication feature is available only between regions in Mainland China and between US (Virginia) and US (Silicon Valley).